Electromagnetic coil array integrated into flat-panel detector

ABSTRACT

Certain embodiments of the present invention provide a flat-panel detector integrated with an electromagnetic coil array. The electromagnetic coil array is positioned inside of the flat-panel detector. The electromagnetic coil array is configured to detect an electromagnetic field at the flat-panel detector. In an embodiment, the flat-panel detector may also include a detector panel. The electromagnetic coil array may be positioned behind the detector panel. In an embodiment, the detector panel may be transparent to electromagnetic fields. In an embodiment, the flat-panel detector may also include a cold plate. The electromagnetic coil array may be positioned between the detector panel and the cold plate. In an embodiment, the electromagnetic coil array may include one or more electromagnetic coils. In an embodiment, the electromagnetic coil array may be a printed circuit board (PCB) electromagnetic coil array.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/611,112, filed Jul. 1, 2003 now U.S. Pat. No. 7,158,754,which is herein incorporated by reference.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[Not Applicable]

MICROFICHE/COPYRIGHT REFERENCE

[Not Applicable]

BACKGROUND OF THE INVENTION

The present invention generally relates to an electromagnetic trackingsystem. In particular, the present invention relates to anelectromagnetic tracking system with an electromagnetic coil arrayintegrated into a flat-panel detector.

Many medical procedures involve a medical instrument, such as a drill, acatheter, scalpel, scope, stent or other tool. In some cases, a medicalimaging or video system may be used to provide positioning informationfor the instrument, as well as visualization of an interior of apatient. However, medical practitioners often do not have the use ofmedical imaging systems when performing medical procedures. Typically,medical imaging systems are too slow to produce useable real-time imagesfor instrument tracking in medical procedures. The use of medicalimaging systems for instrument tracking may be also limited for healthand safety reasons (e.g., radiation dosage concerns), financiallimitations, physical space restrictions, and other concerns, forexample.

Medical practitioners, such as doctors, surgeons, and other medicalprofessionals, often rely upon technology when performing a medicalprocedure, such as image-guided surgery or examination. A trackingsystem may provide positioning information of the medical instrumentwith respect to the patient or a reference coordinate system, forexample. A medical practitioner may refer to the tracking system toascertain the position of the medical instrument when the instrument isnot within the practitioner's line of sight. A tracking system may alsoaid in presurgical planning.

The tracking or navigation system allows the medical practitioner tovisualize the patient's anatomy and track the position and orientationof the instrument. The medical practitioner may use the tracking systemto determine when the instrument is positioned in a desired location.The medical practitioner may locate and operate on a desired or injuredarea while avoiding other structures. Increased precision in locatingmedical instruments within a patient may provide for a less invasivemedical procedure by facilitating improved control over smallerinstruments having less impact on the patient. Improved control andprecision with smaller, more refined instruments may also reduce risksassociated with more invasive procedures such as open surgery.

Tracking systems may also be used to track the position of items otherthan medical instruments in a variety of applications. That is, atracking system may be used in other settings where the position of aninstrument in an object or an environment is unable to be accuratelydetermined by visual inspection. For example, tracking technology may beused in forensic or security applications. Retail stores may usetracking technology to prevent theft of merchandise. In such cases, apassive transponder may be located on the merchandise. A transmitter maybe strategically located within the retail facility. The transmitteremits an excitation signal at a frequency that is designed to produce aresponse from a transponder. When merchandise carrying a transponder islocated within the transmission range of the transmitter, thetransponder produces a response signal that is detected by a receiver.The receiver then determines the location of the transponder based uponcharacteristics of the response signal.

Tracking systems are also often used in virtual reality systems orsimulators. Tracking systems may be used to monitor the position of aperson in a simulated environment. A transponder or transponders may belocated on a person or object. A transmitter emits an excitation signaland a transponder produces a response signal. The response signal isdetected by a receiver. The signal emitted by the transponder may thenbe used to monitor the position of a person or object in a simulatedenvironment.

Tracking systems may be ultrasound, inertial position, orelectromagnetic tracking systems, for example. Electromagnetic trackingsystems may employ coils as receivers and transmitters. Typically, anelectromagnetic tracking system is configured in an industry-standardcoil architecture (ISCA). ISCA uses three colocated orthogonalquasi-dipole transmitter coils and three colocated quasi-dipole receivercoils. Other systems may use three large, non-dipole, non-colocatedtransmitter coils with three colocated quasi-dipole receiver coils.Another tracking system architecture uses an array of six or moretransmitter coils spread out in space and one or more quasi-dipolereceiver coils. Alternatively, a single quasi-dipole transmitter coilmay be used with an array of six or more receivers spread out in space.

The ISCA tracker architecture uses a three-axis quasi-dipole coiltransmitter and a three-axis quasi-dipole coil receiver. Each three-axistransmitter or receiver is built so that the three coils exhibit thesame effective area, are oriented orthogonal to one another, and arecentered at the same point. The exact sizes, shapes, andrelative-to-one-another positions of the transmitter and receivercoil-trios are measured in manufacturing. If the coils are small enoughcompared to a distance between the transmitter and receiver, then thecoil may exhibit dipole behavior. Magnetic fields generated by the trioof transmitter coils may be detected by the trio of receiver coils. Ninetransmitter-receiver mutual inductance measurements may be obtained.From these nine parameter measurements and the information determined inmanufacturing, a position and orientation determination of the receivercoil-trio may be made with respect to the transmitter coil-trio for allsix degrees of freedom.

Some existing electromagnetic tracking systems include a transmitter andreceiver wired to a common device or box. In system with the transmitterand receiver wired to a common device, the object being tracked is wiredto the same device as the components performing the tracking. Thus, therange of motion of the object being tracked is limited.

Wireless electromagnetic tracking systems allow for the object beingtracked to move freely without being limited by connections with thetransmitter or receiver. To reduce the bulk associated with attaching abattery or other power source to a transponder, passive transponders mayemploy a coil as a means of coupling with and receiving power from otherdevices.

Typically, a transponder is located on or within a device in order totrack movement of the device. In order to determine the transponder'slocation, a transmitter generates an excitation signal that is incidenton the transponder. The incidence of the excitation signal on thetransponder causes the transponder to emit a response signal. Typically,the response signal is emitted at the same frequency as the excitationsignal.

The response signal emitted by the transponder and the excitation signalemitted by the transmitter are incident upon a receiving coil.Typically, in a tracking system using a passive transponder theexcitation signal is much larger than the response signal when bothsignals are received at the receiver. Because the response signal isemitted at the same frequency as the excitation signal and the responsesignal is much smaller than the excitation signal, accurately separatingand measuring the response signal is difficult.

When using an electromagnetic tracking system to track the position andorientation of an x-ray detector in a fluoroscope, for example, anelectromagnetic coil array (transmitter or receiver) is typicallymounted on the detector assembly. More particularly, the electromagneticcoil array is typically mounted on the outside of the detector assembly.For example, Anderson et al. (U.S. Pat. No. 6,774,624), Seeley et al.(U.S. Pat. Nos. 6,484,049, 6,490,475, 6,856,826 and 6,856,827), Ferre etal. (U.S. Pat. No. 6,445,943), and Jascob et al. (U.S. Pat No.6,636,757) disclose electromagnetic coil arrays mounted on the outsideof the detector assembly. In particular, Jascob et al. (U.S. Pat. No.6,636,757) provides that “offsetting the set of transmitting coils 62from the shield 54 creates less inteference or cancelling of theelectromagnetic field because of the shield 54, to provide enhancedperformance.” Additionally, Ferre et al. provides that “since thepresence of magnetic material might interfere with the magnetic fieldsthese materials are to be avoided in such an electromagnetic system.”

Furthermore, modern x-ray detectors, such as amorphous siliconflat-panel x-ray detectors, typically do not include enough space formounting an electromagnetic coil array on the inside of the detectorassembly (where the electromagnetic coil array would be in the field ofview of the detector, and thus, most effective). As such, currentelectromagnetic coil arrays typically include a small coverage area andare offset from the detector. Consequently, the patient or detector(including the electromagnetic coil array) must be repositioned severaltimes, thereby inconveniencing the patient and wasting valuable time,money, and other valuable resources.

Thus, a need exists for an electromagnetic coil array in the field ofview of an x-ray detector. More particularly, a need exists for anelectromagnetic coil array integrated into a flat-panel x-ray detector.

BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention provide a flat-paneldetector integrated with an electromagnetic coil array. Theelectromagnetic coil array is positioned inside of the flat-paneldetector. The electromagnetic coil array is configured to detect anelectromagnetic field at the flat-panel detector. In an embodiment, theflat-panel detector may also include a detector panel. Theelectromagnetic coil array may be positioned behind the detector panel.In an embodiment, the detector panel may be transparent toelectromagnetic fields at frequencies below about 40 kilohertz. In anembodiment, the detector panel may be transparent to electromagneticfields at frequencies below about 1 gigahertz. In an embodiment, thedetector panel may be transparent to electromagnetic fields atfrequencies that are transparent to the human body. In an embodiment,the flat-panel detector may also include a cold plate. Theelectromagnetic coil array may be positioned between the detector paneland the cold plate. In an embodiment, the electromagnetic coil array maybe a printed circuit board (PCB) electromagnetic coil array. In anembodiment, the PCB electromagnetic coil array may include one or moreelectromagnetic coils. In an embodiment, the electromagnetic coil arraymay be an electromagnetic receiver. In an embodiment, theelectromagnetic coil array may be an electromagnetic transmitter. In anembodiment, the electromagnetic coil array may be an electromagnetictransceiver. In an embodiment, the electromagnetic coil array mayinclude one or more electromagnetic coils.

Certain embodiments of the present invention provide a method fordetecting an electromagnetic field with a flat-panel detector. Themethod includes integrating an electromagnetic coil array into aninterior portion of the flat-panel detector. The method also includesdetecting the electromagnetic field at the flat-panel detector with theintegrated electromagnetic coil array. In an embodiment, the flat-panelmonitor may include a detector panel. The electromagnetic coil array maybe positioned behind the field of view of the detector panel. In anembodiment, the detector panel may be transparent to the electromagneticfield. In an embodiment, the flat-panel detector may include a coldplate. The electromagnetic coil array may be positioned between thedetector panel and the cold plate. In an embodiment, the electromagneticcoil array may be a printed circuit board (PCB) electromagnetic coilarray. In an embodiment, the PCB electromagnetic coil array may includeone or more electromagnetic coils. In an embodiment, the electromagneticcoil array may be an electromagnetic receiver. In an embodiment, theelectromagnetic coil array may be an electromagnetic transceiver.

Certain embodiments of the present invention provide a printed circuitboard (PCB) electromagnetic coil array integrated in an interior portionof a flat-panel detector. The PCB electromagnetic coil array isconfigured to detect an electromagnetic field at the flat-paneldetector.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an imaging system in accordance with an embodiment ofthe present invention.

FIG. 2 illustrates a tracking system in accordance with an embodiment ofthe present invention.

FIG. 3 illustrates a cross-sectional view of a flat-panel detector withan electromagnetic coil array in accordance with an embodiment of thepresent invention.

FIG. 4 illustrates a flow diagram of a method for detecting anelectromagnetic field with a flat-panel detector in accordance with anembodiment of the present invention.

FIG. 5 illustrates a cross-sectional view of an antiscatter grid with anelectromagnetic coil array in accordance with an embodiment of thepresent invention.

FIG. 6 illustrates a flow diagram of a method for detecting anelectromagnetic field with an antiscatter grid in accordance with anembodiment of the present invention.

FIG. 7 illustrates a flow diagram of a method for using anelectromagnetic coil array as an antiscatter grid in accordance with anembodiment of the present invention.

FIG. 8 illustrates a flow diagram of a method for registering anelectromagnetic coil array with an antiscatter grid in accordance withan embodiment of the present invention.

FIG. 9 illustrates a plan view of a printed circuit boardelectromagnetic coil array in accordance with an embodiment of thepresent invention.

The foregoing summary, as well as the following detailed description ofcertain embodiments of the present invention, will be better understoodwhen read in conjunction with the appended drawings. For the purpose ofillustrating the invention, certain embodiments are shown in thedrawings. It should be understood, however, that the present inventionis not limited to the arrangements and instrumentality shown in theattached drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an imaging system 100 in accordance with anembodiment of the present invention. For purposes of illustration only,the imaging system 100 is described as an x-ray imaging system. Asappreciated by one of ordinary skill in the art, other imaging systemsmay be similarly implemented. The imaging system 100 includes an x-raysource 120 and an x-ray detector 140. An object 160 may also be presentin the imaging system 100.

In an embodiment, the object 160 may be positioned between the x-raysource 120 and the x-ray detector 140. The x-ray source 120 may transmitx-rays to the object 160. The x-ray detector 140 may receive x-rays fromthe object 160. In other words, the x-rays may travel from the x-raysource 120, through the object 160, and to the x-ray detector 140. Asappreciated by one of ordinary skill in the art, the x-rays received bythe x-ray detector 140 may represent the structure of the object 160.

In an embodiment, the detector 140 may include a flat-panel detector,such as the flat-panel detector 300 of FIG. 3.

In an embodiment, the imaging system 100 may also include an antiscattergrid 180, such as the antiscatter grid 400 of FIG. 4. The antiscattergrid 180 may be positioned between the x-ray detector 140 and the object160. As described above, the x-rays may travel from the x-ray source120, through the object 160, and to the x-ray detector 140. The x-raysmay be incident x-rays and/or scattered x-rays. The scattered x-rays mayresult from the presence of the object 160. The antiscatter grid 180 mayfilter the scattered x-rays from the object 160, while allowing theincident x-rays to pass through to the x-ray detector 140. Asappreciated by one of ordinary skill in the art, the difference betweenscattered x-rays, which are filtered, and incident x-rays, which are notfiltered, may be a function of the particular antiscatter grid selected.

In an embodiment, the imaging system 100 may be implemented inconjunction with a tracking system, as described below.

FIG. 2 illustrates a tracking system 200 in accordance with anembodiment of the present invention. For purposes of illustration only,the tracking system 200 is described as an electromagnetic trackingsystem. As appreciated by one of ordinary skill in the art, othertracking systems may be similarly implemented. The tracking system 200includes an electromagnetic transmitter 220 and an electromagneticreceiver 240. An object 260 may also be present in the tracking system200.

In an embodiment, the electromagnetic transmitter 210 may transmit anelectromagnetic field. The electromagnetic field may be an incidentelectromagnetic field and/or a scattered electromagnetic field. Thescattered electromagnetic field may result from the presence of the anobject, such as the object 160 of FIG. 1, being imaged by an imagingsystem, such as the imaging system 100. The electromagnetic receiver 240may receive the electromagnetic field.

In an embodiment, the electromagnetic transmitter 220 and/or theelectromagnetic receiver 240 may include an electromagnetic coil array.The electromagnetic coil array may include one or more electromagneticcoils. In an embodiment, the electromagnetic coil array may beintegrated into a flat-panel detector, such as the flat-panel detector120 of FIG. 1, as described below with respect to the flat-paneldetector 300 of FIG. 3. In an embodiment, the electromagnetic coil arraymay be integrated into an antiscatter grid, such as the antiscatter grid160 of FIG. 1, as described below with respect to the antiscatter grid400 of FIG. 4.

In an embodiment, the tracking system 200 may include one or moreelectromagnetic transmitters 220 and/or one or more electromagneticreceivers 240. In an embodiment, the tracking system 200 may include anelectromagnetic transceiver 260 (not shown). The electromagnetictransceiver 260 may perform the functions of the electromagnetictransmitter 220 and/or the electromagnetic receiver 240. That is, theelectromagnetic transceiver 260 may transmit and/or receive anelectromagnetic field. In an embodiment, the electromagnetic transceiver260 may replace the electromagnetic transmitter 260 and/or theelectromagnetic receiver 240 in the electromagnetic tracking system 200.

FIG. 3 illustrates a cross-sectional view of a flat-panel detector 300with an electromagnetic coil array 320 in accordance with an embodimentof the present invention. The flat-panel detector 300 includes theelectromagnetic coil array 320. In an embodiment, the flat-paneldetector 300 may include a detector panel 340 and a cold plate 360. Asappreciated by one of ordinary skill in the art, the flat-panel detector300 may include other components, such as scintillators, light pipes,beam stops, and/or readout electronics. In an embodiment, the flat-paneldetector 300 may be an amorphous silicon flat-panel detector, forexample.

In an embodiment, the electromagnetic coil array 320 may be anelectromagnetic transmitter, such as the electromagnetic transmitter 220of FIG. 2. In an embodiment, the electromagnetic coil array 320 may bean electromagnetic receiver, such as the electromagnetic receiver 240 ofFIG. 2. In an embodiment, the electromagnetic coil array 320 may be anelectromagnetic transceiver, such as the electromagnetic transceiver 260of FIG. 2.

In an embodiment, the electromagnetic coil array 320 may include one ormore electromagnetic coils. In an embodiment, the electromagnetic coilarray 320 may be a printed circuit board (PCB) electromagnetic coilarray, such as the PCB electromagnetic coil array 900 of FIG. 9. The PCBelectromagnetic coil array may be thin enough to fit within theflat-panel detector. As described below, rigid PCBs or rigid circuitsmay be as thin as about 1 mm to about 2 mm, for example, whereasflexible PCBs or flex circuits may be as thin as 0.1 mm to about 0.2 mm,for example.

In an embodiment, the detector panel 340 may include a plurality ofdetector elements, such as photodiodes. In an embodiment, the detectorpanel 340 may include glass, for example. In an embodiment, the detectorpanel 340 may include non-conductive components, such as non-conductivecoatings. In an embodiment, the detector panel 340 may include partiallyconductive components, such as partially conductive coatings. In anembodiment, the detector panel 340 may not include any highly conductivecomponents.

In an embodiment, the cold plate 340 may include metal, such asstainless steel and/or aluminum. In an embodiment, the cold plate 340may include one or more coolant channels. For example, water, ethyleneglycol, and/or other coolant may be pumped through the cooling channelsin the cold plate 340 to cool the flat-panel detector 300.

In an embodiment, the electromagnetic coil array 320 may be positionedinside of the flat-panel detector 300. In an embodiment, theelectromagnetic coil array 320 may be positioned behind the detectorpanel 340 in the flat-panel detector 300. More particularly, theelectromagnetic coil array 320 may be positioned behind the field ofview of the detector panel 340, for example, with respect to an x-raysource, such as the x-ray source 120 of FIG. 1. In an embodiment, theelectromagnetic coil array 320 may be positioned between the detectorpanel 340 and the cold plate 360 in the flat-panel detector 300.

In an embodiment, the detector panel 340 may be transparent toelectromagnetic fields. More particularly, the detector panel 340 may betransparent to electromagnetic fields because the detector panel may notinclude any highly conductive materials, as described above. Thedetector panel 340 may be transparent to electromagnetic fields withfrequencies less than about 40 kHz, for example. The detector panel 340may be transparent to electromagnetic fields with frequencies less thanabout 1 GHz, for example. The detector panel 340 may be transparent toelectromagnetic fields with frequencies that are also transparent to thehuman body, for example. Consequently, the operation of theelectromagnetic coil array 320 may not interfere with operation of theflat-panel detector 300.

In an embodiment, the electromagnetic fields may be alternating current(AC) and/or pulsed direct current (PDC), for example.

FIG. 4 illustrates a flow diagram of a method 400 for detecting anelectromagnetic field with a flat-panel detector in accordance with andembodiment of the present invention. The method 400 includes integratingan electromagnetic coil array in an interior portion of the flat-paneldetector 410 and detecting the electromagnetic field at the flat-paneldetector with the integrated electromagnetic coil array 420.

At step 410, the electromagnetic coil array may be integrated in aninterior portion of the flat-panel detector, as described above.

At step 420, the electromagnetic field at the flat-panel detector may bedetected with the integrated electromagnetic coil array, as describedabove.

As will be appreciated by those of skill in the art, certain steps maybe performed in ways other than those recited above and the steps may beperformed in sequences other than those recited above.

FIG. 5 illustrates a cross-sectional view of an antiscatter grid 500with an electromagnetic coil array 520 in accordance with an embodimentof the present invention. The antiscatter grid 500 includes theelectromagnetic coil array 520. In an embodiment, the antiscatter grid500 may include one or more strips 540 and one or more interspacers 560.As appreciated by one of ordinary skill in the art, the antiscatter grid500 may include other components. In an embodiment, the antiscatter grid500 may be an x-ray antiscatter grid, such as the antiscatter grid 160of FIG. 1.

In an embodiment, the electromagnetic coil array 520 may be anelectromagnetic transmitter, such as the electromagnetic transmitter 220of FIG. 2. In an embodiment, the electromagnetic coil array 520 may bean electromagnetic receiver, such as the electromagnetic receiver 240 ofFIG. 2. In an embodiment, the electromagnetic coil array 520 may be anelectromagnetic transceiver, such as the electromagnetic transceiver 260of FIG. 2.

In an embodiment, the electromagnetic coil array 520 may include one ormore electromagnetic coils. In an embodiment, the electromagnetic coilarray 520 may be a printed circuit board (PCB) electromagnetic coilarray, such as the PCB electromagnetic coil array 900 of FIG. 9.

In an embodiment, the strips 540 may include x-ray opaque materials,such as lead. In an embodiment, the interspaces 560 may include x-raytransparent materials, such as aluminum. In an embodiment, theantiscatter grid 500 may be a strip grid, for example. That is, thestrips 540 may be positioned to form a grid that is substantiallyparallel in orientation and either substantially horizontal orsubstantially vertical in direction. In an embodiment, the antiscattergrid 500 may be cross grid, for example. That is, the strips 540 may bepositioned to form a grid that is substantially parallel in orientationand both substantially horizontal and substantially vertical indirection. In an embodiment, the interspacers 560 may be positionedbetween the strips 540. In an embodiment, the antiscatter grid 500 maybe an antiscatter grid available from Soyee Products, Incorporated(Danielson, Conn.).

In an embodiment, the electromagnetic coil array 520 may be positionedin front of the antiscatter grid 500. More particularly, theelectromagnetic coil array 520 may be positioned in front of the fieldof view of the antiscatter grid 500, for example, with respect to anx-ray source, such as the x-ray source 120 of FIG. 1.

In an embodiment, the electromagnetic coil array 520 may be positionedbehind the antiscatter grid 500. More particularly, the electromagneticcoil array 520 may be positioned behind the field of view of theantiscatter grid 500, for example, with respect to an x-ray source, suchas the x-ray source 120 of FIG. 1.

In an embodiment, the electromagnetic coil array 520 may be attached tothe antiscatter grid 500.

In an embodiment, the electromagnetic coil array 520 may be registeredwith the antiscatter grid 500. That is, the electromagnetic coil array500 may be positioned such that the operation of the electromagneticcoil array 520 does not interfere with the operation of the antiscattergrid 500. In other words, incident x-rays allowed to pass through theantiscatter grid 500 may also pass through the electromagnetic coilarray 520. Conversely, scattered x-rays filtered or blocked by theantiscatter grid 500 may also be filtered or blocked by theelectromagnetic coil array 520.

FIG. 6 illustrates a flow diagram of a method 600 for detecting anelectromagnetic field with an antiscatter grid in accordance with andembodiment of the present invention. The method includes integrating anelectromagnetic coil array with an antiscatter grid 610 and detectingthe electromagnetic field at the antiscatter grid with the integratedelectromagnetic coil array 620. The electromagnetic coil array may beregistered with the antiscatter grid.

At step 610, the electromagnetic coil array may be integrated with theantiscatter grid, as described above.

At step 620, the electromagnetic field at the antiscatter grid may bedetected with the integrated electromagnetic coil array, as describedabove.

As will be appreciated by those of skill in the art, certain steps maybe performed in ways other than those recited above and the steps may beperformed in sequences other than those recited above.

FIG. 7 illustrates a flow diagram of a method 700 for using anelectromagnetic coil array as an antiscatter grid in accordance with anembodiment of the present invention. The method 700 includes providingthe electromagnetic coil array and filtering scattered x-rays with theelectromagnetic coil array.

At step 710, an electromagnetic coil array may be provided. Theelectromagnetic coil array may be the electromagnetic coil array 500 ofFIG. 5. The electromagnetic coil array may be a printed circuit board(PCB) electromagnetic coil array, such as the PCB electromagnetic coilarray 900 of FIG. 9. The PCB electromagnetic coil array may include asubstrate, such as the substrate 940 of FIG. 9, and one or more tracks,such as the tracks 560 of FIG. 9. The substrate may be transparent tox-rays. The tracks may be opaque to x-rays.

At step 720, scattered x-rays may be filtered by the electromagneticcoil array, while incident x-rays may pass through the electromagneticcoil array. That is, the electromagnetic coil array may function as theantiscatter grid, such as the antiscatter grid 180 of FIG. 1 or theantiscatter grid 500 of FIG. 5.

As will be appreciated by those of skill in the art, certain steps maybe performed in ways other than those recited above and the steps may beperformed in sequences other than those recited above.

FIG. 8 illustrates a flow diagram of a method 800 for registering anelectromagnetic coil array with an antiscatter grid in accordance withan embodiment of the present invention. The method 800 includespositioning the antiscatter grid and the electromagnetic coil array inthe imaging system 810, acquiring an image of the antiscatter grid andthe electromagnetic coil array 820, and determining that theelectromagnetic coil array is registered with the antiscatter grid basedat least in part on the acquired image 830. In an embodiment, the method800 may also include repositioning the antiscatter grid and/or theelectromagnetic coil array in the imaging system 840.

At step 810, the antiscatter grid and the electromagnetic coil array maybe positioned in the imaging system. The antiscatter grid may be theantiscatter grid 160 of FIG. 1 or the antiscatter grid 500 of FIG. 5.The electromagnetic coil array may be the electromagnetic coil array 520of FIG. 5 or the printed circuit board (PCB) electromagnetic coil array900 of FIG. 9. The imaging system may be the imaging system 100 ofFIG. 1. As described above, the antiscatter grid may be positionedindependent of the electromagnetic coil array. Conversely, theelectromagnetic coil array may be attached to the antiscatter grid.

At step 820, an image of the antiscatter grid and the electromagneticcoil array may be acquired. More particularly, the image of theantiscatter grid and the electromagnetic coil array may be acquired bythe imaging system, such as the imaging system 100 of FIG. 1. Theantiscatter grid and the electromagnetic coil array may be an object,such as the object 160 of FIG. 1.

At step 830, a determination that the electromagnetic coil array isregistered with the antiscatter grid may be based at least in part onthe acquired image of the antiscatter grid and the electromagnetic coilarray. In a low resolution image, for example, a moire patterns may bevisible when the electromagnetic coil array is not registered with theantiscatter grid. In a high resolution image, the electromagnetic coilarray may be visible when the electromagnetic coil array is notregistered with the antiscatter grid.

At step 840, the antiscatter grid and/or the electromagnetic coil arraymay be repositioned in the imaging system. More particularly, if theelectromagnetic coil array is not registered with the antiscatter grid,then the antiscatter grid and/or the electromagnetic coil array may berepositioned in the imaging system. The steps 820-840 of the method 800may be repeated as necessary until the electromagnetic coil array isregistered with the antiscatter grid.

As will be appreciated by those of skill in the art, certain steps maybe performed in ways other than those recited above and the steps may beperformed in sequences other than those recited above.

FIG. 9 illustrates a plan view of a printed circuit board (PCB)electromagnetic coil array 900 in accordance with an embodiment of thepresent invention. The PCB electromagnetic coil array 900 includes asubstrate 940 and one or more tracks 960. As appreciated by one ofordinary skill in the art, the PCB electromagnetic coil array 900 mayinclude other PCB components. Anderson (U.S. patent application Ser. No.11/611,112), herein incorporated by reference, provides an example ofthe PCB electromagnetic coil array 900.

In an embodiment, the substrate 940 may include rigid materials, such asepoxy-fiberglass composites (i.e., fiberglass in an epoxy resin binder)and/or other rigid materials. For example, the substrate 940 may includeG-10 and/or FR-4, both of which are available from Rogers Corporation(Rogers, Conn.).

In an embodiment, the substrate 940 may include flexible materials, suchas polymer films and/or other flexible materials. For example, thesubstrate 940 may include polyester films, such as Mylar®, and/orpolyamide films, such as Kapton®, both available from DuPont(Circleville, Ohio). Printed circuit boards made with completelyflexible and partially flexible substrates are commonly referred to as aflex circuits and rigid-flex circuits, respectively.

In an embodiment, the substrate 940 may include (electrically)non-conductive materials. For example, all of the rigid and flexiblesubstrate materials may also be (electrically) non-conductive.

In an embodiment, the tracks 960 may include (electrically) conductivematerials, such as copper, aluminum, gold and/or silver. Gold and/orsilver tracks may be more expensive and more difficult to process thanother (electrically) conductive materials.

In an embodiment, the tracks 960 may include spirals, such as square,rectangle, circle, triangle, and/or other shaped spirals.

In an embodiment, the tracks 960 of the PCB electromagnetic coil array900 may form one or more electromagnetic coils.

In an embodiment, the tracks 960 may be attached to the substrate 940,for example, by a photolithographic process, a microwire process, and/ora handwire process. In a subtraction process, for example, copper foilmay be glued to a substrate 940 and then etched to form copper tracks960. In an addition process, for example, aluminum may be sputtered ontoa substrate 940 in a vacuum chamber to form aluminum tracks 960. Inanother addition process, for example, glue may be applied to thesubstrate 940 and then wire may be attached to the substrate 940 withthe glue to form the tracks 960.

As described above, the PCB electromagnetic coil array 900 may beintegrated into a flat-panel detector, such as the flat-panel detector300 of FIG. 3.

As described above, the PCB electromagnetic coil array 900 may beintegrated into an antiscatter grid, such as the antiscatter grid 400 ofFIG. 4. In an embodiment, the substrate 940 may be an x-ray transparentsubstrate. The x-ray transparent characteristics of the substrate 940may depend on the substrate material. For example, all of the rigid,flexible, and (electrically) non-conductive substrate materials may alsobe x-ray transparent. The x-ray transparent characteristics of thesubstrate 940 may depend on the substrate thickness. The substrate 940may be x-ray transparent at thicknesses less than about 2 mm. Thesubstrate 940 may be x-ray transparent at thicknesses less than 1 mm.

As described above, the PCB electromagnetic coil array 900 may beregistered with an antiscatter grid, such as the antiscatter grid 400 ofFIG. 4. More particularly, the substrate 940 of the PCB electromagneticcoil array 900 may be registered with the interspacers 460 of theantiscatter grid 400. That is, incident x-rays allowed to pass throughthe interspacers 460 may also pass through the substrate 940.Additionally, the tracks 960 of the PCB electromagnetic coil array 900may be registered with the strips 440 of the antiscatter grid 400. Thatis, scattered x-rays filtered by the strips 440 may also be filtered bythe tracks 960. In other words, the substrate 940 and the tracks 960 maybe positioned such that the operation of the PCB electromagnetic coilarray 900 does not interfere with the operation of the antiscatter grid400.

An imaging system, such as the imaging system 100 of FIG. 1, may beutilized to determine if the electromagnetic coil array 420 isregistered with the antiscatter grid 400. In an embodiment of thepresent invention, the antiscatter grid 400 may be visible with a highresolution imaging system. If the electromagnetic coil array 420 is notvisible when introduced into the high resolution imaging system, thenthe electromagnetic coil array 420 is registered with the antiscattergrid 400. Conversely, if the electromagnetic coil array 420 is notvisible when introduced into the imaging system, then theelectromagnetic coil array may not be registered with the antiscattergrid 400.

Yatsenko et al. (U.S. patent application Ser. No. 11/271,604), hereinincorporated by reference, provides a system and method for integrationof a calibration target into a c-arm. More particularly, Yatsenko et al.teaches intrinsic geometry calibration using moire patterns produced byexisting x-ray system components. If the antiscatter grid is used tolocate the x-ray source in the x-ray image coordinates, the tracker coilarray may be inherently pre-registered to the x-ray image, and thus, thetracker coordinates may be registered with the image coordinates.

In an embodiment, the PCB electromagnetic coil array 900 may function asan antiscatter grid, such as the antiscatter grid 400 of FIG. 4. Thatis, incident x-rays may pass through the substrate 940, while scatteredx-rays may be filtered by the tracks 960. As described above, thesubstrate 940 may be x-ray transparent, thus allowing incident x-rays topass through the PCB electromagnetic coil array 900. The tracks 960 maybe x-ray opaque, thus filtering scattered x-rays. More particularly, thex-ray opaque properties of the tracks 960 may depend on the trackmaterial and/or the track thickness. For example, lead tracks greaterthan about 1 mm in thickness may be sufficient to filter scatteredx-rays, and thus, allow the PCB electromagnetic coil array 900 tofunction as an antiscatter grid.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

1. A flat-panel detector including: a detector panel; and anelectromagnetic coil array integrated with the flat-panel detector,wherein the electromagnetic coil array is inside the flat-paneldetector, wherein the electromagnetic coil array is configured to detectan electromagnetic field at the flat-panel detector, and wherein theelectromagnetic coil array is behind the detector panel.
 2. Theflat-panel detector of claim 1, wherein the detector panel istransparent to electromagnetic fields at frequencies below about 40kilohertz.
 3. The flat-panel detector of claim 1, wherein the detectorpanel is transparent to electromagnetic fields at frequencies belowabout 1 gigahertz.
 4. The flat-panel detector of claim 1, wherein thedetector panel is transparent to electromagnetic fields at frequenciesthat are transparent to the human body.
 5. The flat-panel detector ofclaim 1, further including a cold plate, wherein the electromagneticcoil array is between the detector panel and the cold plate.
 6. Theflat-panel detector of claim 1, wherein the electromagnetic coil arrayis a printed circuit board (PCB) electromagnetic coil array.
 7. Theflat-panel detector of claim 6, wherein the PCB electromagnetic coilarray includes at least one electromagnetic coil.
 8. The flat-paneldetector of claim 1, wherein the electromagnetic coil array is anelectromagnetic receiver.
 9. The flat-panel detector of claim 1, whereinthe electromagnetic coil array is an electromagnetic transmitter. 10.The flat-panel detector of claim 1, wherein the electromagnetic coilarray is an electromagnetic transceiver.
 11. The flat-panel detector ofclaim 1, wherein the electromagnetic coil array includes at least oneelectromagnetic coil.
 12. A method for detecting an electromagneticfield with a flat-panel detector, the method including: integrating anelectromagnetic coil array in an interior portion of the flat-paneldetector, wherein the flat-panel detector includes a detector panel, andwherein the electromagnetic coil array is behind the field of view ofthe detector panel; and detecting the electromagnetic field at theflat-panel detector with the integrated electromagnetic coil array. 13.The method of claim 12, wherein the detector panel is transparent to theelectromagnetic field.
 14. The method of claim 12, wherein theflat-panel detector includes a cold plate and wherein theelectromagnetic coil array is between the detector panel and the coldplate.
 15. The method of claim 12, wherein the electromagnetic coilarray is a printed circuit board (PCB) electromagnetic coil array. 16.The method of claim 15, wherein the PCB electromagnetic coil arrayincludes at least one electromagnetic coil.
 17. The method of claim 12,wherein the electromagnetic coil array is an electromagnetic receiver.18. The method of claim 12, wherein the electromagnetic coil array is anelectromagnetic transceiver.
 19. A printed circuit board (PCB)electromagnetic coil array integrated in an interior portion of aflat-panel detector, the PCB electromagnetic coil array configured todetect an electromagnetic field at the flat-panel detector, wherein theflat-panel detector includes a detector panel, and wherein theelectromagnetic coil array is behind the field of view of the detectorpanel.